Grants related:
General
This project aims at the searching, observation and analysis of massive stars in nearby galaxies to provide a solid empirical ground to understand their physical properties as a function of those key parameters that gobern their evolution (i.e. mass, spin, metallicity, mass loss, and binary interaction).
Massive stars are central objects to Astrophysics. Born with at least 8 solar masses, their evolution proceeds very fast, yielding large amounts of nuclear processed material by means of strong stellar winds (loosing up to 90% of their initial mass before facing a violent death as Supernova) and emitting intense radiation fields. Despite their scarcity, massive stars play a decisive role in many aspects of the evolution of the Cosmos (e.g. they are primary agents of the chemical and dynamical evolution of galaxies and have been proposed as key agents in the reionization of the Universe). Along their complex evolution, they are associated with the most extreme stellar objects (O-type and WR stars; blue and red supergiants; luminous blue variables; massive stellar black holes, neutron stars and magnetars; massive X- and gamma-ray binaries). They are also the origin of newly studied phenomena such as long-duration GRBs or the recently detected gravitational waves produced by a merger of two massive black holes or neutron stars. From a practical perspective, massive stars have become invaluable indicators of present-day abundances and distances in external galaxies, even beyond the Local Group. In addition, the interpretation of the light emitted by H II regions and starburst galaxies relies on our knowledge of the effect that the strong ionizing radiation emitted by these hot stellar objects produces on the surrounding interstellar medium.
This project aims at the searching, observation and analysis of massive stars in nearby galaxies to provide a solid empirical ground to understand their physical properties as a function of those key parameters that gobern their evolution (i.e. mass, spin, metallicity, mass loss, and binary interaction). In this endeavour, the project benefits from best quality observations obtained with the last generation of facilities available at the Canary and the ESO observatories, as well as other observations of interest provided from space missions such as Gaia, HST, IUE and TESS. Samples with a few to several hundreds of individual massive stars in different evolutionary stages and metallicity environments are then analyzed with the last generation of stellar atmosphere codes and optimized tools for the quantitative spectroscopic analysis of massive stars to extract as much empirical information as possible about stellar+wind parameters, surface abundances and spectroscopic variability.
The main research lines presently active in the project are:
- the observation and analysis of large samples of massive OB stars in the Milky Way;
- the exploration of the hidden population of massive stars in the Milky Way;
- the searching, observation and analysis of massive extragalactic stars, with special emphasis in those found in low metallicity galaxies;
- the development and use of model atmospheres, model atoms and numerical tools for the analysis of massive stars.
Members
Results
Highlights 2020
1. The IACOB project presents empirical evidence of the scarcity of Galactic O-type stars with masses 40-80 Msol close to the theoretical zero age main sequence. Th reason of this result could be indicating that the accretion rate of mass during the stars formation process of massive stars could be lower than traditionally considered.
2. Presented empirical evidence of the existence of multiple star forming bursts in the Cygnus OB2 massive star formation region. The way is paved for the first in-depth study of the massive star population of the Cygus-X region in the Milky Way benefiting from the WEAVE survey.
3. Studied membership and kinematical properties in a sample of 80 blue and red supergiants in the PerOB1 association by using high resolution multi-epoch spectroscopy and Gaia astrometry data. A forthcoming spectroscopic study of this sample of star will provide new empirical clues to improve our understanding of massive stars evolution.
4. The MAMSIE-IACOB collaboration presents first in-depth study of the pulsational propeties of a large sample of massive Galactic OB-type stars by means of the combined study of high-resolution spectroscopic data from HERMES, FIES and SONG and high cadence photometric data provide by the TESS mission.
5. Estimated that the binarity fraction for evolved high-mass stars (red supergiants) should be at least 0.15±0.03.
6. Identified the first strong candidate to be a super-AGB star in the Galaxy (VX Sgr).
Scientific activity
Related publications
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HST/STIS spectroscopy of the magnetic Of?p star HD 108: the low state at ultraviolet wavelengthsWe present the first ultraviolet spectrum of the peculiar, magnetic Of?p star HD 108 obtained in its spectroscopic low state. The new data, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope, reveal significant changes compared to IUE spectra obtained in the high state: N Vλ1240, Si IVλ1400 and C IVλ1550Marcolino, W. L. F. et al.
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52012 -
Discovery of a young and massive stellar cluster. Spectrophotometric near-infrared study of Masgomas-1Context. Recent near-infrared data have contributed to the discovery of new (obscured) massive stellar clusters and massive stellar populations in previously known clusters in our Galaxy. These discoveries lead us to view the Milky Way as an active star-forming machine. Aims: The main purpose of this work is to determine physically the mainRamírez-Alegría, S. et al.
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52012 -
Blue Luminous Stars in Nearby Galaxies—UIT 005: A Possible Link to the Luminous Blue Variable StageA detailed study of the blue supergiant UIT 005 (B2-2.5Ia+) in M 33 is presented. The results of our quantitative spectral analysis indicate that the star is a very luminous (log L/L sun ~ 5.9 dex) and massive (M ~ 50 M sun) object, showing a very high nitrogen-to-oxygen ratio in its surface (N/O~8, by mass). Based on the derived Mg and SiUrbaneja, M. A. et al.
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72011 -
Wind Diagnostic from Infrared LinesFor the large population of massive stars lying behind dust, among which are the youngests and potentially the most massive of our Galaxy, none of the commonly used wind diagnostics can be applied. As an alternative, a few observable infrared hydrogen lines are strong enough to hold wind diagnostics similarly to Hα. Using current state-of-the-artLenorzer, A. et al.
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62008 -
Observational Evidence for a Correlation Between Macroturbulent Broadening and Line-profile Variations in OB SupergiantsThe spectra of O and B supergiants (Sgs) are known to be affected by a significant form of extra line broadening (usually referred to as macroturbulence) in addition to that produced by stellar rotation. Recent analyses of high-resolution spectra have shown that the interpretation of this line broadening as a consequence of large-scale turbulentSimón-Díaz, S. et al.
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92010 -
Is macroturbulent broadening in OB Supergiants related to pulsations?The spectrum of O and B Supergiants is known to be affected by an important extra line-broadening (usually called macroturbulence) that adds to stellar rotation. Recent analysis of high resolution spectra has shown that the interpretation of this line-broadening as a consequence of large-scale turbulent motions would imply highly super-sonicSimón-Díaz, S. et al.
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122010 -
Field O stars: formed in situ or as runaways?A significant fraction of massive stars in the Milky Way and other galaxies are located far from star clusters and star-forming regions. It is known that some of these stars are runaways, i.e. possess high space velocities (determined through the proper motion and/or radial velocity measurements), and therefore most likely were formed in embeddedGvaramadze, V. V. et al.
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82012 -
Fluorescent Excitation of Balmer Lines in Gaseous Nebulae: Case DNonionizing stellar continua are a potential source of photons for continuum pumping in the hydrogen Lyman transitions. In the environments where these transitions are optically thick, de-excitation occurs through higher series lines. As a result, the emitted flux in the affected lines has a fluorescent contribution in addition to the usualLuridiana, V. et al.
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22009 -
WSO and the winds of massive stars: the gate to the metal-poor Local UniverseThe spectrographs on-board the World Space Observatory (WSO) will provide access to the 1020-1800 Å wavelength range with unprecedented sensitivity. Previous observatories operating in the 1150-2000 Å range (such as IUE and HST-STIS) have proved extremely useful to study the winds of OB type stars, which leave their most prominent imprints in theGarcia, M. et al.
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92011 -
The young stellar population of IC 1613. II. Physical properties of OB associationsContext. To understand the structure and evolution of massive stars, systematic surveys of the Local Group galaxies have been undertaken, to find these objects in environments of different chemical abundances. We focus on the metal-poor irregular galaxy IC 1613 to analyze the stellar and wind structure of its low-metallicity massive stars. WeGarcía, M. et al.
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112010 -
The young stellar population of IC 1613. I. A new catalogue of OB associationsContext: Determining the parameters of massive stars is crucial to understand many processes in galaxies and the Universe, since these objects are important sources of ionization, chemical enrichment and momentum. 10m class telescopes enable us to perform detailed quantitative spectroscopic analyses of massive stars in other galaxies, samplingGarcia, M. et al.
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82009 -
The VLT-FLAMES Tarantula Survey. I. Introduction and observational overviewThe VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, including optical and near-infrared photometry andEvans, C. J. et al.
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62011 -
The nature of V39: an LBV candidate or LBV impostor in the very low metallicity galaxy IC 1613?Context. Very few examples of luminous blue variable (LBV) stars or LBV candidates (LBVc) are known, particularly at metallicities below that of the Small Magellanic Cloud (SMC). The LBV phase is known to be crucial for the evolution of massive stars, and its behavior with metallicity is very poorly known. Variable star V39 in IC 1613 is a wellHerrero, A. et al.
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42010 -
The Araucaria Project: VLT-spectroscopy of blue massive stars in NGC 55Aims: This is the first paper of a series devoted to studying the population of blue massive stars in NGC 55, a galaxy of the Sculptor group at a distance of about 2 Mpc. Methods: We have obtained optical (3300{-}6210 Å), low-resolution spectra of approximately 200 blue massive stars with VLT-FORS2, which we have classified with the aid of MilkyCastro, N. et al.
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72008 -
The ARAUCARIA project: Grid-based quantitative spectroscopic study of massive blue stars in NGC 55Context. The quantitative study of the physical properties and chemical abundances of large samples of massive blue stars at different metallicities is a powerful tool to understand the nature and evolution of these objects. Their analysis beyond the Milky Way is challenging, nonetheless it is doable and the best way to investigate their behaviorCastro, N. et al.
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62012 -
Pursuing Local Group blue massive stars with WSO-ISSISThe Local Group galaxies enable us to study the impact of metallicity on the structure and evolution of massive stars through spectroscopic analyses. However, color-based target selection for spectroscopy (in absence of known spectral types), though relatively successful, usually produces lists dominated by B-type modest-mass stars. We haveGarcía, M.
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92011 -
On the nature of candidate luminous blue variables in M 33Context. Luminous blue variables (LBVs) are a class of highly unstable stars that have been proposed to play a critical role in massive stellar evolution as well as being the progenitors of some of the most luminous supernovae known. However the physical processes underlying their characteristic instabilities are currently unknown. Aims: In orderClark, J. S. et al.
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52012 -
A peculiar Of star in the Local Group galaxy IC 1613Context. Results from the theory of radiatively driven winds are nowadays incorporated in stellar evolutionary and population synthesis models, and are used in our interpretation of the observations of the deep Universe. Yet, the theory has been confirmed only until Small Magellanic Cloud metallicities. Observations and analyses of O-stars at lowerHerrero, A. et al.
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72012 -
The complex structure of HH 110 as revealed from Integral Field SpectroscopyHH 110 is a rather peculiar HerbigHaro object in Orion that originates due to the deflection of another jet (HH 270) by a dense molecular clump, instead of being directly ejected from a young stellar object. Here we present new results on the kinematics and physical conditions of HH 110 based on Integral Field Spectroscopy. The 3D spectral dataLópez, R. et al.
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82010 -
Integral field spectroscopy of the brightest knots of HH 223 in L723HH 223 is the optical counterpart of a larger scale H2 outflow, driven by the protostellar source VLA 2A, in L723. Its poorly collimated and rather chaotic morphology suggested Integral Field Spectroscopy (IFS) as an appropriate option to map the emission in order to derive the physical conditions and kinematics. Here we present new results basedLópez, R. et al.
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82012
